This invention relates to systems which deliver electrical power to a subassembly of electronic devices, such as a subassembly of one or more integrated circuit chips on a printed circuit board, thru pressed electrical contacts. Each such contact includes two mating terminals that get pressed together.
In a conventional printed circuit board of the prior art, electrical power is received thru a connector that is attached to one edge of the board. Typically, the connector has several cylindrical-shaped pins that slide into corresponding holes of a socket which is mounted to a backplane. Electrical power from a power supply travels along conductors in the backplane to the socket, and then travels through the pins and along conductors on the printed circuit board to the electronic devices.
However, a problem with the above conventional practice is that the conductors which couple the electronic devices on the printed circuit board to the power supply inherently have a parasitic capacitance, a parasitic inductance, and a parasitic resistance. Those parasitic parameters limit the ability of the power supply to keep the voltage constant at the electronic devices.
One way to reduce the above parasitic parameters is to shorten the conductors which couple the electronic devices to the power supply. This can be achieved by mounting the power supply on a second printed circuit board which is held parallel to the printed circuit board that holds the electronic devices; providing mating electrical terminals on two surfaces of the printed circuit boards that face each other; and pressing mating terminals together.
But, if the above two printed circuit boards somehow get misaligned, the open circuits or abnormally high resistances can occur between the mating terminals. In that case, the power supply will again be unable to properly deliver power to the electronic devices.
Accordingly, a primary object of the present invention is to overcome the above problem.
A power system, which constitutes one preferred embodiment of the present invention, includes a power supply that has an output voltage terminal and an output voltage feedback terminal. The output voltage terminal is coupled by a first conductor to one pressed power contact which is then coupled by a second conductor to an electronic device. Also, the electronic device is coupled by a third conductor to one pressed signal contact which is then coupled by a fourth conductor to the output voltage feedback terminal on the power supply.
Further, and in accordance with the present invention, the power system includes a fault detection circuit which is coupled to the fourth conductor. In operation, the fault detection circuit senses if the pressed signal contact is open at a time when the pressed signal contact is supposed to be closed. If an open contact is sensed, the fault detection circuit sends a signal to an operator which indicates that corrective action is needed.
Preferably, the power supply and the fault detection circuit are mounted on a first printed circuit board; the electronic device is mounted on a second printed circuit board; and the pressed power contact as well as the pressed signal contact lie on two surfaces that face each other on the first and second printed circuit boards. This structure enables the power supply to be very close to the electronic device; and that enables the first, second, third and fourth conductors to be short. Thus, the parasitic capacitance, parasitic inductance and parasitic resistance of those conductors will be small; and in addition, any open circuit fault in the pressed signal contact will be detected.